Drive for step switches for regulating transformers, chokes and the like



April 19, 1966 H. BRUCKHOFF 3,247,333

DRIVE FOR STEP SWITCHES FOR REGULATING TRANSFORMERS, CHOKES AND THE LIKE 2 Sheets-Sheet 1 Filed April. 11, 1963 arwvwfw Hams Bruekhoff p 1966 H. BRUCKHOFF 3, 47,333

DRIVE FOR STEP SWITCHES FOR REGULATING TRANSFORMERS, CHOKES AND THE LIKE Filed April 11. 1963 2 Sheets$heet 2 Fig.3

gvwmbo'b Hams Brucklqov f 3% 12%,, JWs Q my enem United States Patent 3,247,333 DRIVE FOR STEP SWITCHES FOR REGULATING TRANSFORMERS, CHGKES AND THE LIKE Hans Bruckhoff, Wangen an der Aare, Switzerland, assignor to Brown, Bovcri & Company Limited, Baden, Switzerland, a joint-stock compan Filed Apr. 11, 1963, Ser. No. 272,451 Claims priority, application Switzerland, Apr. 19, 1962, 4,800/62 6 Claims. ((11. 2tl0-11) The invention concerns a tap changing device for regulating transformers, reactance coils, and the like, with transfer switches actuated by a jump drive, socalled jump transfer switches, and tap selector switches, whereby the jump transfer switches and tap selectors are provided with gears which act on the drive.

With tap changing devices, the movable switching contacts of the tap selectors with stationary counter switching contacts arranged on two tracks and connected to the taps on the winding, are driven by an intermittent gear which is in the form of a Maltese cross movement or a roller gear. For the latter it has been proposed to use a compulsory blocking device for the end position or a disengageable blocking device for the individual steps. When such selectors operate in conjunction with a load transfer switch with a jump drive, the driving side of the jump drive for the transfer switch is coupled either directly or by means of a simple spur or bevel gear to the driven side of the intermittent gear. With these known tap changing devices the difficulty arises that the common outer drive has to be brought exactly into the position of rest after each switching-over operation so that the jump action of the transfer switch and the position of engagement of the tap selector contact pieces are in agreement.

A considerable improvement is, however, possible with the new arrangement. In accordance with the invention it is proposed that the gear possesses a planetary drive with a crank pin located eccentrically on a planet wheel, whereby the pin is connected mechanically to the driving side of the jump transfer switch.

FIG. 1 shows a constructional example of the new arrangement.

FIG. 2 is the diagram of connections which is referred to in the description of FIG. 1.

FIG. 3 shows a further diagram of connections for a modified method of operation of the arrangement according to FIG. 1.

In FIG. 1 the fixed contacts of the tap selector belonging to one circular track are indicated by l, 3, 5, 7, 9, 1i. and those of a second circular track by 2, 4, 6, it), 12. Reference numeral 11b indicates the movable contact piece of the coarse selector which cooperates with stationary contact pieces 12a and 13. The movable contact 15 of the selector which is associated with the odd number fixed contact pieces is in constant electrical connection with the slip-ring 17, whose lead 19 is located inside the hollow shaft 21, which in turn carries the contact piece 15. Similarly, the movable contact piece 14- is associated with the even-number fixed contact pieces and its slip-ring 16 is connected to the lead llfi which is also located inside the hollow shaft 21. Contact piece 14 is carried by the hollow shaft 20 which surrounds the hollow shaft 21 concentrically. Shaft 21 is rigidly connected to gear Wheel 23 and shaft 20 to gear wheel 22. Gear wheels 22 and 23 mesh with gear Wheels 24 and 25 respectively, which in turn are joined by short shafts to gear wheels 26 and 27, the latter meshing with gear wheels 28 and 29 respectively. The external drive of the tap changing drive which is not shown engages the driving shaft 33. at the coupling point 30, this shaft passing through the casing wall 32 (for example of a transformer) in a known manner. The driving shaft 31 is connected at its lower end to a gear wheel 33 which engages a gear wheel 34. The wheel 34 is fixed to the lower end of shaft 35 and gear wheel 36 to the upper end of this shaft. Gear wheel 36 meshes with planet wheel 37 and the latter with a toothed wheel rim 3% which is inside the gear casing 39. Planet Wheel 37 is fixed on a shaft 40 the upper end of which is offset and constructed in the form of a crank pin 41. Numeral 42 indicates the path followed by a point on the crank pin axis, this being in the form of a hypocycloid with four reversal points a, b, c, d. The planet wheel shaft 40 engages loosely with a hole in a driving disc 43 which is loosely mounted on shaft 35 and is provided with an arcuate slot 44 having a length corresponding to an angular rotation of 180 of the shaft 45. Shaft 45 is rigidly joined to the stopping and cam wheels 46, 47 which in turn are loosely mounted on shaft 35. Gear wheels 28 and 29 are arranged on auxiliary shafts 48 and 49 respectively which are supported in the casing 39 and carry the roller pairs 50 and 51 which are mutually displaced by 90", the lower pairs being at the same level as disc 47 and the upper pairs at the same level as disc 46. The auxiliary shafts 48 and 49 as well as the roller pairs 50 and 51 are arranged symmetrically with reference to shaft 35.

The crank pin 41 is connected by the rod 52 to lever 53 which is fixed to the driving shaft 54 of the jump transfer switch 55. This switch 55 is located inside a casing 56 and is not shown in FIG. 1. The leads 1%, 19 for the tap selector pass through the casing 56 in an insulated manner at the points 57, 58. The other electrical connections between the tap selector contacts 1 to 12, from the coarse selector contacts 11b, 12a, 13 to the regulating winding, and also the latter are for the sake of simplicity not shown in FIG. 1 (see FIG. 2). The hollow shaft 21 carries the stopping and cam wheels 59, 60 for actuating the coarse selector. The movable contact piece 11b is connected by way of shaft 61, wheel 62, driving belt 63, wheel 64, to the auxiliary shaft which carries the rollers 66 and 67, the upper group 66 being in the plane of disc 59 and the lower group in the plane of disc 60. It is to be noted that the various wheels and discs are shown in FIG. 1 with a much greater spacing in the axial direction than is actually the case in order to make the assembly clearer. In the actual construction these elements are arranged closely together in the form of a packet which occupies very little space.

The electrical diagram for the tap changing device of FIG. 1 is shown in FIG. 2, whereby the same reference numbers are used for corresponding elements. The tap selector contacts 1 to 12 are connected to the corresponding winding taps To to 12a and the coarse selector contact r 13 to the tap 13a of the coarse step. For the jump transfer switch 55 a known construction with five switching elements 55a to 55 and two change-over resistors 55g and 55h has been chosen by way of example, the output side of the tap changing device being indicated at u.

The method of operation of the arrangement is as follows: It is assumed that the position of the tap changing device shown in the drawing has been reached after a previous downward regulation where the selector contact 15 has moved from tap 9:: (FIG. 2) to 11a and the transfer switch 55 from lead 13 to lead N. For the next switching operation in the downward direction, it is necessary that first of all selector contact 14 should be moved to contact 12 and the transfer switch be then connected to lead 18. For this purpose, by means of the external drive which is not shown and is coupled at 30 to the device, the main driving shaft 31 is rotated in the direction indicated by the arrow, whereby by means of gear wheels 33, 34, shaft 35, gear wheel 36, planet wheel 37 in contact with the stationary spur ring 38, a rotational clockwise movement commences which causes the crank pin 41, starting from point a on the path 42, to move in the direction of the arrow to point 12. This movement of the crank pin 41 is imparted to the driving shaft 54 of the jump transfer switch 55 by the rod 52 and lever 53. In the position shown, the jump mechanism of the transfer switch is released and lever 53 is in its right-hand end position. When the crank pin 41 reaches the point of reversal b on its path 42, lever 53 and thus shaft 54 are at about the middle of their angular movement and this corresponds to about the half-released condition of the transfer switch jump mechanism. Simultaneously, by means of planet wheel shaft 40 and driving disc 43, shaft 45 and stopping and cam wheels 46, 47 are caused to rotate in the direction indicated by the arrow. Thus disc 47 by means of its cam 47:: and disc 46 by means of the corresponding recess after a short movement take along the roller pairs 50 and by way of auxiliary shaft 48 and gear wheels 28, 26, 24, 22 cause the hollow shaft 20 and thus selector contact 14 to rotate. For a complete change-over of the selector contact 14 from contact 10 to 12 half a rotation of the discs 46, 47 is required, whereby a second driving movement of the roller pairs 50 by means of the cam 47b of disc 47 and the corresponding recess in disc 46 occurs. Due to the cooperation of the discs 46, 47 with the roller pairs 50 which occurs twice, the movement of the selector contact 14 takes place in a special manner, namely first of all it slowly leaves the fixed contact 1t) and then moves rapidly into a mid-position, the last part of this movement occurring however at a reduced speed, whereupon it remains in this position for a time and finally moves away from this position in a similar manner in order to establish contact with the next fixed contact 12. During this change-over operation of the tap selector contact 14, crank pin 41 moves from point a on the path 42, where the crank arm forms a dead centre position with the rod 52, over point b to point on the path 42 where a dead centre position also occurs. The jump change-over of the transfer switch 55 thus occurs for instance shortly before the reversal point 0 is reached, after the switch 14 of the tap selector is already in engagement with the fixed contact 12. The change-over sequence of the individual switching elements 55a to 55 (FIG. 2) of the transfer switch 55 occurs in a known manner, namely 55c opens, 55:: closes, 55b closes and 550 of the other change-over contact closes. The change-over of switching element 550 can occur relatively slowly, whilst the other switching elements operate in rapid succession with a sudden or jump action.

When a further tapchange in the downward direction of regulation is required, planet wheel shaft 46 and discs 46, 47 are given a further half rotation by the outer drive. Whilst thus the crank pin passes along the path 42 from point 0 over point d to point a, the cams 47a and 47b of disc 47 and the corresponding recesses in disc 46 act one after another on the roller pairs 51. In an analogous manner to that already described, the changeover of the contact 15 from tap 11 to tap 1 now occurs by way of gear wheels 2?, 27, 25, 23 and hollow shaft 21. Transfer switch 55 then operates at an instant when the crank pin 41 is for instance shortly before point a on the path 42. Prior to this, however, the movable contact 11b of the coarse selector must be brought on to fixed contact 13 which is connected to tap 13a (FIG. 2). This is achieved by means of discs 59, 60 and rollers 66, 67, shaft 65, pulley 64, belt 63, pulley 62 and shaft 61. The winding part 120, 13a (FIG. 2) is so dimensioned that due to the series connection with the winding part 1a to lie: when compared with tap 12a just one tap jump is achieved.

For regulation in the upward direction the external drive is actuated in the reverse direction. All rotational movements then occur in the opposite direction to that indicated by the arrows. Starting from the position shown in FIG. 2, it is then only necessary to change over the jump transfer switch 55 from the lead 19 to the lead 18, without a selector contact being moved. For this purpose the driving disc 43 has an arcuate slot 44 whereby the shaft 45 is only carried along after half an idle rotation of the disc. During this movement, the crank pin 41 travels along the path 42 from point a over point d to point 0, whereby the load change-over occur's' some= what sooner. On further upward regulation, the sequence of events is as already described except that the direction of rotation of the parts in question is reversed.

The arrangement described also allows another method of operation for a tap changing device to be used where according to FIG. 3 each winding tap is always connected to two fixed switching contacts. In FIG. 3 the taps 1 to 6 are connected on the one hand to the contacts 1a to 6a and on the other hand to the contact series 1b to 6b. The other parts 14 to 19 and 55 correspond to those of FIGS. 1 and 2. For such a tap changing device where one jump transfer switch operates together with two tap selectors which in the tap positions are in contact with fixed contacts which are connected to the same tap, it hasalready been proposed that during a regulating operation the movable contacts of the tap selectors should have such a contact sequence that the contact which is the last to reach a certain fixed contact should be the first to leave it again and vice versa. This is briefly explained by means of FIG. 3. Thus during an upward regulation, contact 14 is the last to reach the contact 5a. When passing to tap 4, the contact 14 passes from the position shown in FIG. 3 to the fixed contact 4a without being under current. Then transfer switch 55 changes over to lead 18 and finally contact 15 moves from 5b to 4b. When passing on to tap 3, contact 15 is first brought to 3b in a current-free state and so on. The advantage of this engagement sequence is that the transfer switch does not have to make any intermediate switching operation which would otherwise be necessary with the usual alternating step sequence. The method of operation just described can be realised with the new arrangement in a most simple manner when for the continuous position at the taps, points b and d on the path 42 are selected for the transfer switch. As already described, at these points the jump mechanism of the transfer switch is in a semireleased condition. There is no reaction on the external drive because at points b, d the rod 52, due to the hypocycloidal shape of path 42, is practically perpendicular to the latter. The arrangement of the fixed selector contacts 1a to 6a and 1b to 6]) must of course be as shown in FIG. 3. From the manner of movement of the tap selector contacts 14 and 15 described in connection with FIG. 1, it will be obvious that thus the slow departure from the fixed contact, for instance, 5a, and the smooth approach to the next contact, for instance 4a, is assured.

In order to adapt the device to suit the number of fixed contacts, that is the number of taps, it is possible in accordance with the invention to construct the gears 24, 26 and 25, 27 as variable speed gears, whereby the transmission ratio can be altered on the selector arms without having to make any changes in the rest of the tap changing device. The parallel arrangement of the gear and tap selector shafts avoids the necessity of providing any direction-changing devices, so that the mechanical stresses occurring in the device are reduced to a minimum. The arrangement shown in FIG. 1 can in certain cases be modified by providing separate gears for the transfer switch and selector switches instead of a single common gear. In this case the connection between the planet Wheel shaft 40 and the driving disc 43 is omitted. The gear wheel pairs 33, 34 can be arranged above the gear wheel 36, this being easily possible by providing the upper end of shaft 36 with an extension. Driving disc 43 can also be built as a gear wheel which is driven by a further gear wheel having a corresponding number of teeth and located for instance on the main shaft 31.

The new arrangement possesses the advantage that two different methods of operation for tap changing devices with jump transfer switches are possible whilst using to a very great extent the same elements. By using a speed change gear the device can be adapted in a very simple manner to suit various numbers of taps and tap steps. The production of such apparatus is thus very economical. The compact assembly enables a considerable saving in space to be achieved, especially with multi-phase devices.

What I claim is:

1. In a drive mechanism for changing taps on electrical apparatus such as regulating transformers, chokes and the like, the combination comprising a jump transfer switch having a plurality of switching elements cooperative with two rotary tap selector switches, each said tap selector switch having a rotary contact arm and a plurality of stationary contacts engageable in succession by said contact arm, circuit means connecting said stationary contacts of said tap selector switches to the taps on said electrical apparatus and connecting said contact arms with the switching elements of said jump transfer switch, a main rotatable drive shaft, an externally toothed driving gear secured upon said drive shaft, a stationary internally toothed ring gear concentric with and surrounding said driving gear, a planet gear intermediate and meshed with said driving and ring gears, a driving disc arranged concentrically on but not secured to said drive shaft, said driving disc having a concentric 180 arcuate slot therein, a shaft extending from said planet gear and which includes a crank arm thereon, said planet gear shaft being secured to said driving disc for rotating the same as said planet gear rotates about the axis of said driving gear, a pair of cam discs arranged concentrically on but not secured to said drive shaft, a drive shaft for and secured to said cam discs, said cam disc driving shaft being located laterally of said main driving shaft and being extended into said arcuate slot in said driving disc, a pair of auxiliary drive shafts mounted for rotation about their respective axes, each said auxiliary drive shaft including thereon one cam follower means cooperative with one of said cam discs, and another cam follower means cooperative with the other said cam disc, the two said cam follower means on each said auxiliary drive shaft being mutually displaced by 90 and serving to rotate their respective auxiliary drive shafts when said cam discs are rotated by their common drive shaft by a drive coupling established between said common drive shaft and said arcuate slot in said driving disc after a rotation of said driving disc, means respectively connecting said auxiliary drive shafts with said rotary contact arms of said tap selector switches, and means connecting said crank arm to said switching elements for actuating said switching elements between their closed and open positions.

2. A drive mechanism as defined in claim 1 for changing taps on electrical apparatus wherein said planet gear and the crank arm on the planet gear shaft are arranged such that the axis of said crank arm describes a closed hypocycloid path with four reversal points for one complete revolution of said planet gear.

3. A drive mechanism as defined in claim 1 for changing taps on electrical apparatus wherein said connecting means between said crank arm and said switching elements includes a drive rod, one end of which is connected to said crank arm and the other end being connected to a lever secured upon a drive shaft which actuates said switching elements.

4. A drive mechanism as defined in claim 3 for changing taps on electrical apparatus wherein saidplanet gear, crank arm and drive rod have a combined motion such that for each limit position of said lever and drive shaft actuating said switching elements, said crank arm is located approximately at the reversal points of the hypocycloidal path whereby said drive rod together with crank arm form a dead center.

, 5. A drive mechanism as defined in claim 1 for changing taps on electrical apparatus wherein said means connecting said auxiliary drive shafts with said rotary contact arms of said tap selector switches include an adjustable speed gearing.

6. A drive mechanism as defined in claim 1 for changing taps on electrical apparatus wherein all of said shafts are arranged parallel to one another.

References Cited by the Examiner UNITED STATES PATENTS 1,980,220 11/1934- Morton.

2,484,576 10/ 1949 Minneci 200-l1 X 2,693,573 11/1954 Perkins 32243.5

FOREIGN PATENTS 850,924 9/ 1939 France.

KATHLEEN H. CLAFFY, Primary Examiner.

0 BERNARD A. GILHEANY, Examiner.

D. SMITH, Assistant Examiner. 

1. IN A DRIVE MECHANISM FOR CHANGING TAPS ON ELECTRICAL APPARATUS SUCH AS REGULATING TRANSFORMERS, CHOKES AND THE LIKE, THE COMBINATION COMPRISING A JUMP TRANSFER SWITCH HAVING A PLURALITY OF SWITCHING ELEMENTS COOPERATIVE WITH TWO ROTARY TAP SELECTOR SWITCHES, EACH SAID TAP SELECTOR SWITCH HAVING A ROTARY CONTACT ARM AND A PLURALITY OF STATIONARY CONTACTS ENGAGEABLE IN SUCCESSION BY SAID CONTACT ARM, CIRCUIT MEANS CONNECTING SAID STATIONARY CONTACTS OF SAID TAP SELECTOR SWITCHES TO THE TAPS ON SAID ELECTRICAL APPARATUS AND CONNECTING SAID CONTACT ARMS WITH THE SWITCHING ELEMENTS OF SAID JUMP TRANSFER SWITCH, A MAIN ROTATABLE DRIVE SHAFT, AN EXTERNALLY TOOTHED DRIVING GEAR SECURED UPON SAID DRIVE SHAFT, A STATIONARY INTERNALLY TOOTHED RING GEAR CONCENTRIC WITH AND SURROUNDING SAID DRIVING GEAR, A PLANET GEAR INTERMEDIATE AND MESHED WITH SAID DRIVING AND RING GEARS, A DRIVING DISC ARRANGED CONCENTRICALLY ON BUT NOT SECURED TO SAID DRIVE SHAFT, SAID DRIVING DISC HAVING A CONCENTRIC 180* ARCUATE SLOT THEREIN, A SHAFT EXTENDING FROM SAID PLANET GEAR AND WHICH INCLUDES A CRANK ARM THEREON, SAID PLANET GEAR SHAFT BEING SECURED TO SAID DRIVING DISC FOR ROTATING THE SAME AS SAID PLANET GEAR ROTATES ABOUT THE AXIS OF SAID DRIVING GEAR, A PAIR OF CAM DISCS ARRANGED CONCENTRICALLY ON BUT NOT SECURED TO SAID DRIVE SHAFT, A DRIVE SHAFT FOR AND SECURED TO SAID CAM DISCS, SAID CAM DISC DRIVING SHAFT BEING LOCATED LATERALLY OF SAID MAIN DRIVING SHAFT AND BEING EXTENDED INTO SAID ARCUATE SLOT IN SAID DRIVING DISC, A PAIR OF AUXILIARY DRIVE SHAFTS MOUNTED FOR ROTATION ABOUT THEIR RESPECTIVE AXES, EACH SAID AUXILIARY DRIVE SHAFT INCLUDING THEREON ONE CAM FOLLOWER MEANS COOPERATIVE WITH ONE OF SAID CAM DISCS, AND ANOTHER CAM FOLLOWER MEANS COOPERATIVE WITH THE OTHER SAID CAM DISC, THE TWO SAID CAM FOLLOWER MEANS ON EACH SAID AUXILIARY DRIVE SHAFT BEING MUTUALLY DISPLACED BY 90* AND SERVING TO ROTATE THEIR RESPECTIVE AUXILIARY DRIVE SHAFTS WHEN SAID CAM DISCS ARE ROTATED BY THEIR COMMON DRIVE SHAFT BY A DRIVE COUPLING ESTABLISHED BETWEEN SAID COMMON DRIVE SHAFT AND SAID ARCUATE SLOT IN SAID DRIVING DISC AFTER A 180* ROTATION OF SAID DRIVING DISC, MEANS RESPECTIVELY CONNECTING SAID AUXILIARY DRIVE SHAFTS WITH SAID ROTARY CONTACT ARMS OF SAID TAP SELECTOR SWITCHES, AND MEANS CONNECTING SAID CRANK ARM TO SAID SWITCHING ELEMENTS FOR ACTUATING SAID SWITCHING ELEMENTS BETWEEN THEIR CLOSED AND OPEN POSITIONS. 